Ema — 2019

Ema formed from a disturbance several hundred nautical miles southwest of the main Hawaiian Islands and became a tropical depression early on 12 October 2019. It strengthened quickly that day and reached tropical storm strength around 1200 UTC 12 October, then moved generally northward and northwestward. Increasing upper‑level wind shear caused the storm to lose its deep convection and weaken; Ema fell to a tropical depression by 1800 UTC 13 October and became a post‑tropical remnant low by 0600 UTC 14 October. The system dissipated a few days later while well west of the Hawaiian Islands. There were no direct landfalls on the main Hawaiian Islands. Ema moved northward toward parts of the Papahānaumokuākea Marine National Monument in the northwest Hawaiian Islands, prompting a Tropical Storm Watch issued at 2100 UTC 12 October for the area from Nihoa to French Frigate Shoals to Maro Reef. All watches were discontinued by 2100 UTC 13 October as the cyclone weakened. Ema’s maximum sustained winds were estimated at 45 knots (about 52 mph) with a minimum central pressure near 1003 mb, corresponding to a moderate tropical storm at peak intensity around 1800 UTC 12 October. Satellite microwave and scatterometer data supported the peak intensity estimate; no ship or surface reports of tropical‑storm‑force winds were recorded. Observed storm surge and rainfall impacts were minimal to none in the main Hawaiian Islands; the report lists no specific surge heights or notable rainfall totals at named cities or counties. No ship or land stations measured tropical‑storm‑force winds associated with Ema. There were no reports of damage or casualties (no direct or indirect deaths) attributed to Ema. The storm’s impacts were negligible given its short lifespan and distance from populated islands. Noteworthy items include the relatively rapid organization and brief intensification to 45 kt shortly after formation, which was not well anticipated by forecasts. Genesis was not predicted in advance in the Tropical Weather Outlooks, and official track errors were larger than the recent 5‑year mean, though intensity forecasts correctly anticipated a short‑lived cyclone that would weaken as shear increased.